3 years ago

Working mechanism of post-acting polycarboxylate superplasticizers containing acrylate segments

Working mechanism of post-acting polycarboxylate superplasticizers containing acrylate segments
Biqin Dong, Feng Xing, Liran Zhang, Xiangming Kong, Fang Wang
Acrylate-containing polycarboxylate superplasticizers were synthesized by copolymerizing acrylic acid, α-methallyl-ω-methoxy poly(ethylene glycol) ether, and acrylic esters [hydroxyethyl acrylate (HEA) or hydroxypropyl acrylate (HPA)]. Their dispersing effects and fluidity-retaining capabilities were evaluated by spread tests of cement pastes. The temperature sensitivity of the performance was especially focused upon. It was found by Fourier transform infrared spectroscopy and specific anionic charge density measurements that the ester groups in the acrylate-containing copolymers hydrolyze in alkaline conditions, and thus additional RCOO− groups are continuously produced. The gradual production of RCOO− leads to increasing charge density and hence increasing adsorption of the polymer on the cement surface. The hydrolysis of HEA units is slightly faster than of HPA units in the corresponding copolymers. By this mechanism, a post-acting, or delayed, dispersing effect is realized. Such post-acting polymers alone or formulated with normal polycarboxylate superplasticizer can be used achieve a long fluidity retention of fresh concrete, especially under elevated temperatures. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 135, 45753.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/app.45753

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